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Message-ID: <20f447a438aa98afb18be4642c8888b3@codeaurora.org>
Date: Mon, 16 Nov 2020 09:42:13 +0800
From: Can Guo <cang@...eaurora.org>
To: Bart Van Assche <bvanassche@....org>
Cc: asutoshd@...eaurora.org, nguyenb@...eaurora.org,
hongwus@...eaurora.org, ziqichen@...eaurora.org,
rnayak@...eaurora.org, linux-scsi@...r.kernel.org,
kernel-team@...roid.com, saravanak@...gle.com, salyzyn@...gle.com,
Stanley Chu <stanley.chu@...iatek.com>,
"James E.J. Bottomley" <jejb@...ux.ibm.com>,
"Martin K. Petersen" <martin.petersen@...cle.com>,
Matthias Brugger <matthias.bgg@...il.com>,
open list <linux-kernel@...r.kernel.org>,
"moderated list:ARM/Mediatek SoC support"
<linux-arm-kernel@...ts.infradead.org>,
"moderated list:ARM/Mediatek SoC support"
<linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH RFC v1 1/1] scsi: pm: Leave runtime resume along if block
layer PM is enabled
Hi Bart,
Resent, typo fixed.
On 2020-11-15 04:57, Bart Van Assche wrote:
> On 11/12/20 10:30 PM, Can Guo wrote:
>> If block layer runtime PM is enabled for one SCSI device, then there
>> is
>> no need to forcibly change the SCSI device and its request queue's
>> runtime
>> PM status to active in scsi_dev_type_resume(), since block layer PM
>> shall
>> resume the SCSI device on the demand of bios.
>
> Please change "along" into "alone" in the subject of this patch (if
> that
> is what you meant).
>
Aha, sorry, a typo here.
>> + if (scsi_is_sdev_device(dev)) {
>> + struct scsi_device *sdev;
>>
>> + sdev = to_scsi_device(dev);
>
> A minor comment: I think that "struct scsi_device *sdev =
> to_scsi_device(dev);" fits on a single line.
>
Sure.
>> + * If block layer runtime PM is enabled for the SCSI device,
>> + * let block layer PM handle its runtime PM routines.
>
> Please change "its runtime PM routines" into "runtime resume" or
> similar. I think that will make the comment more clear.
>
Yes, thanks.
>> + if (sdev->request_queue->dev)
>> + return err;
>> + }
>
> The 'dev' member only exists in struct request_queue if CONFIG_PM=y so
> the above won't compile if CONFIG_PM=n. How about adding a function in
> include/linux/blk-pm.h to check whether or not runtime PM has been
> enabled?
>
You are right.
> Otherwise this patch looks good to me.
>
Actually, I am thinking about removing all the pm_runtime_set_active()
codes in both scsi_bus_resume_common() and scsi_dev_type_resume() - we
don't need to forcibly set the runtime PM status to RPM_ACTIVE for
either
SCSI host/target or SCSI devices.
Whenever we access one SCSI device, either block layer or somewhere in
the path (e.g. throgh sg IOCTL, sg_open() calls
scsi_autopm_get_device())
should runtime resume the device first, and the runtime PM framework
makes
sure device's parent (and its parent's parent and so on)gets resumed as
well.
Thus, the pm_runtime_set_active() seems redundant. What do you think?
Thanks,
Can Guo.
> Thanks,
>
> Bart.
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